Cahokia Mounds, Collinsville IL

Cahokia Mounds State Historic Site (IL) is located a few miles east of St. Louis MO near Collinsville IL. It is a 2200 acre site that preserves the central section of the largest prehistoric Indian city north of 
Mexico. The site on the rich soil of the flood 
plains of the Mississippi and Missouri Rivers, the 
culture survived for several hundred years until 
it was gradually abandoned after about 1300 A. D.

Because of the sheer magnitude of the mounds and the site, it is difficult to take good pictures from the ground.  This is Monk's Mound from about a quarter mile away.  The steps allow visitors to climb the mound.

This is called Monk's Mound.  It is the largest prehistoric earthen structure in the New World.  It is about 100 feet high and was built in 4 tiers over a period of 300 years.  The base is 14 acres in area and an estimated 22 million cubic feet of earth were dug and moved by hand from nearby "borrow pits" to build it.  At the top, there was a building about 105 feet long by 48 feet wide and 50 feet high which was home to the principal leader of the group and the seat of government.

 

There are generally 3 types of mounds on the site. Flat top mounds usually were the bases for buildings, while conical topped or ridge topped mounds were either boundary markers or burial mounds.

Cahokia is named for a sub-tribe of the Illinois Confederacy who populated the area before the French arrived in the late 1600s. It is frequently referred to as the "City of the Sun". That name derives from sun symbolism on some artifacts, and the existence of sun calendars on the site.

This last photo is called Woodhenge and is a solar calendar similar the the more famous one in England, Stonehenge. 

                              

The outer circle of wooden poles is on a 410 foot diameter. Important solar events, such as 

equinoxes, are marked by sighting across the center pole to the appropriately placed outer 

poles. Note Monk's Mound in the background about a half mile away.